Vascular disease remains one of the leading causes of morbidity and mortality worldwide. Drugs targeting conventional risk factors lower part of the vascular risk. However, experimental and clinical data suggest that other novel factors may explain the greater part of the risk for coronary, cerebral and peripheral arterial diseases and their clinical manifestations.
Dysregulated uptake of oxidatively modified low density lipoprotein (LDL) particles (oxLDL) by vascular cells mediated by scavenger receptors is considered to be a crucial step in atherogenesis. In addition to mediating the uptake of oxidized lipids, the scavenger receptors can mediate activation of pro-oxidant and pro-inflammatory signaling pathways which are involved in activation of endothelial cells and macrophages, and which lead to progression of atherosclerosis and plaque erosion/rupture as well as to microvascular dysfunction with impaired tissue perfusion and oxygen delivery/utilization, resulting in myocardial or lower limb ischemia.
The lectin-like oxidized low density lipoprotein receptor 1 (LOX-1) is a multifunctional scavenger receptor which is expressed on vascular endothelial cells, monocytes and macrophages, vascular smooth muscle cells, and platelets. LOX-1 binds oxLDL and other oxidized lipids, resulting in activation of NADPH oxidase and generation of reactive oxygen species including superoxide anion. Superoxide anion inactivates endothelial nitric oxide and activates MAP kinase and NF-κB. This in turn induces expression of inflammatory adhesion molecules, cytokines and chemokines, as well as matrix metalloproteinases and pro-apoptotic mediators.
The pro-inflammatory, pro-oxidant and pro-apoptotic consequences of oxLDL-LOX-1 mediated signaling in endothelial cells, smooth muscle cells, and macrophages are thought to play a key role in progression of atherosclerosis and plaque instability and may also play a role in impaired tissue perfusion and oxygen delivery, resulting in ischemia. The clinical consequences of advanced atherosclerosis and organ ischemia include: acute coronary syndromes, myocardial infarction, unstable angina, stroke, angina, claudication and critical limb ischemia. In addition, oxidative stress, vascular inflammation and resulting microvascular dysfunction are thought to contribute to diabetic vascular disease, including nephropathy and retinopathy.
While basal LOX-1 endothelial expression levels are relatively low under normal physiological conditions, vascular LOX-1 expression is upregulated in conditions associated with vascular disease. Endothelial LOX-1 levels have been shown to be increased by oxidative stress, pro-inflammatory cytokines, C-reactive protein (CRP) and angiotensin II. LOX-1 is also upregulated in the endothelium of atherosclerotic and diabetic animals and in monocytes/macrophages isolated from patients with vascular disease. Hyperglycemia, advanced glycated endproducts and atherogenic lipoproteins also upregulate LOX-1 expression, providing a specific molecular mechanistic link between diabetes and vascular complications.
The upregulation of LOX-1 by cytokines and CRP also suggests a link between conventional vascular risk factors and accelerated vascular disease in high risk patients and diabetics. Both CRP and soluble LOX-1 are elevated in patients with acute coronary syndromes. In vitro data have shown that anti-LOX-1 antibodies prevent CRP mediated monocyte adhesion to human aortic endothelial cells, further supporting a role for LOX-1 as an adhesion molecule relevant to vascular inflammation (Li et al., Circulation Research 2004, 95: 877-883).
Increased expression of LOX-1 coupled to elevated levels of oxLDL and other oxidized lipoproteins induces endothelial dysfunction, in part, by activating NADPH oxidase and generation of reactive oxygen species. Experimentally, oxidant stress induced endothelial dysfunction can be reversed with a neutralizing anti-LOX-1 antibody in ApoE-knockout mice (Xu et al., Arteriosclerosis, Thrombosis and Vascular Biology 2007, 27:871-877). In this study, anti-LOX-1 antibody increased both bioavailable nitric oxide and eNOS protein expression.
Experimental in vivo data indicate that overexpression of vascular and macrophage LOX-1 in the presence of oxidized lipids contributes to atherosclerosis and microvascular dysfunction by activating pro-oxidant and pro-inflammatory signaling pathways. Thus, inhibition of LOX-1 is expected to prevent development and progression of atherosclerosis and its acute complications such as acute coronary syndromes, myocardial infarction and unstable angina. In addition LOX-1 inhibition is also expected to ameliorate microvascular dysfunction, preventing clinical manifestations of tissue ischemic such as chronic angina, refractory angina, claudication and critical limb ischemia.
LOX-1 inhibition is useful not only in the treatment and prevention of atherosclerotic vascular disease, but also in treatment of other pathologic conditions characterized by oxidative stress and inflammation such as rheumatoid arthritis, various forms of vasculitis, uveitis, age related macular degeneration, and prevention of cardiovascular events in autoimmune diseases (e.g. lupus erythematosis, psoriasis).
In summary, experimental and clinical data suggest that LOX-1 may be the critical oxidized lipid receptor linking oxidative stress, inflammation and vascular disease. The anti-LOX-1 antibodies and antigen binding fragments described in this invention inhibit binding of oxLDL and other oxidized lipids/lipoproteins to LOX-1, preventing activation of LOX-1, thereby reducing vascular oxidative stress and inflammation. These antibodies are expected to prevent and ameliorate the acute and chronic manifestations of vascular disease and to prevent and ameliorate other diseases characterized by oxidative stress and inflammation.